Vitreous surgeries performed on the eye of a patient suffering from diabetic retinopathy, macular pigment degeneration, or vitreous hemorrhage, which are leading causes of loss of sight, are performed by mounting a contact lens for vitreous surgery of the cornea by way of an ophthalmic viscoelastic substance in order to clearly observe the interior of the eye under a operation microscope. The surgeon holds in his dexterous hand a vitreous cutter, vertical scissors, or other intraocular operative instrument, and holds in his non-dexterous hand an intraocular illumination guide connected to a light source apparatus via an optical fiber. In this manner, since only one hand can be used in the intraocular operation (hereinafter referred to as “one-hand method”), skill is required and the operation requires a considerable length of time.
For example, in the procedure for detaching the inner limiting membrane of the topmost layer of the retina, or detaching a proliferative membrane, which is one cause of retinal detachment, from the retina, the surgeon must maintain a very high level of concentration over a long period of time. When the procedure is performed from the peripheral portion of the ocular fundus inside the eye to the most peripheral portion of the ocular fundus, the iris becomes an obstacle and the area to be treated can not be viewed from the pupil. Therefore, a surgeon's assistant must press the area to be treated from the exterior of the eyeball toward the interior of the eyeball, and when pressure cannot be applied in the manner that surgeon desires, the surgeon and assistant both experience stress.
A method is being studied that allows the surgeon to perform intraocular procedures using both hands (hereinafter referred to as the “two-hand method”), whereby an illumination apparatus (extraocular illumination) mounted on a surgical microscope is used in lieu of a fiber illumination source that is inserted into the eye in order to illuminate the inside of the eye via the cornea and the contact lens for vitreous surgery. However, a portion of the illumination light reflects from the surface of the lens, the surgeon experiences glare, and the quality of the ocular fundus image is reduced by the reflected light.
The quantity of light directed into the eye by the extraocular illumination source described above is low in comparison with the quantity of intraocular illumination. Therefore, a more distinct ocular fundus image must be obtained by reducing the reflective loss on the surface of the lens and increasing, even by a small amount, the light rays transmitted through the contact lens for vitreous surgery.
An antireflection film disposed on the contact lens for vitreous surgery preferably has an antireflective effect that extends over a range that is as wide as possible in the visible light region of 400 nm to 780 nm in order to obtain a naturally colored observation image.
Initially, the inventors provided an antireflective coating using vacuum deposition, which is widely used for intraocular lens and the like, in order to first coat an antireflective film on a contact lens for vitreous surgery. The reflection of illumination light is reduced, but the vacuum-deposited film is not highly durable to washing, disinfectants, and sterilizing high-pressure steam, and repeated use as a surgical lens was not possible.
Contact lenses for vitreous surgery and lenses for intraocular observation have lengthy contact with water, corrosive medicines, and sterilizing high-pressure steam; the contact surface area is considerable; and the temperature at the time of contact is high in comparison with environments in which lens used in spectacles, cameras, binoculars, microscopes, and other optical instruments are employed. In other words, an antireflective film coated onto a contact lens for vitreous surgery and a lens for intraocular observation have a much greater need for high durability in comparison with the durability required in an antireflective film for the optical equipment described above.
With conventionally used vacuum deposition and ordinary sputtering, it is difficult to obtain durability performance required in a lens for intraocular observation and a contact lens for vitreous surgery, even if the film formation substance and film composition are changed. For example, Patent Document 1 proposes a moisture proof antireflection film that has a high refractive index layer composed of HfO2 and Ta2O5, and a low refractive index layer composed of SiO2.    [Patent Document 1] Japanese Laid-open Patent Application No. 7-234302